The restless mind cannot think of the transcendental Reality without the help of a concrete symbol. The student is asked to imagine four parts in Brahman, or Cosmic Reality. They are called four quarters. The first three - gross, subtle, and casual - constitute the phenomenal world. The fourth, so called only in relation to the three just mentioned, is transcendental, being beyond time, space, and casualty. It is Turiya, or the unconditioned Brahman and Atman are identical. The gross aspect of Brahman has its counterpart in the waking state (Visva) of Atman, when the external world is perceived by means of the sense-organs; the subtle aspect, in the dream state (Taijasa), when the internal world, created by waking experiences, is perceived; and the causal aspect, in deep sleep (Prajna [dreamless sleep]), characterised by bliss and the cessation of mental activity. The transcendental aspect of Atman, or Pure Consciousness, which is Its true nature, is the same as Turiya. (Swami Nikhilananda: The Upanishads Volume 2, p.209)

When a person realises his self to be Turiya, he is freed from craving for outer objects. He is freed from the false fear and false expectation which plague phenomenal life. When one knows the true nature of the desert, one no longer runs after the illusory water of the mirage, and when one knows the true nature of the rope, one is not frightened by the idea of the snake falsely superimposed upon it. The realisation of the self as Turiya destroys ignorance, desire, attachment, aversion, etc. Turiya does not lie outside the three states. It is their unchanging and unrelated substratum. A mirage cannot be perceived without the substratum of a desert.

The three states are unreal, like the illusory snake in the rope. When the truth is known, one realises that the snake is nothing but the rope; likewise, with the Knowledge of Turiya, one realises that the three states are nothing but Brahman, or Pure Consciousness. (p.237)